IL21 and Parkinson disease: We have not found the significant difference in the serum concentrations of IL-21 between PD patients and HCs [39.55 (35.15–45.21), 95%CI (36.75, 43.88) vs. 42.42 (33.15–47.15), 95%CI (37.38, 45.68), P = 0.588, Figure 4C], we have also not found the significant difference in the serum concentrations of TGF-β between PD patients and HCs [3,545.86 (2,612.3–4,333.03), 95%CI (2,971.69, 3,899.70) vs. 3,580.06 (2,868.06–4,441.79), 95%CI (3,202.30, 3948.81), P = 0.841, Figure 4D].